Aviation Accident Summaries

Aviation Accident Summary WPR21FA258

Missoula, MT, USA

Aircraft #1




The pilot and passenger departed on a personal flight to an unknown destination. The airplane’s weight for the flight was about 68 pounds above the maximum gross takeoff weight. The airplane proceeded westward, overflew rising mountainous terrain, and entered a box canyon. The last recorded data point, about 3.3 miles east of the accident site, showed that the airplane was at an altitude of about 678 ft above ground level; on a magnetic heading of 271°; and at a groundspeed of 68 knots, which was 17 knots faster than the published stall speed. The airplane impacted terrain in a low-energy, nose-low attitude, and nearly vertical descent with a small debris field, consistent with an aerodynamic stall. High-density altitude conditions at the departure airport prevailed, and no turbulence, low-level wind shear, or obscurations existed near the accident site. The available evidence for this investigation precluded a determination of whether the airplane continued to climb and maintained its airspeed as it progressed toward higher terrain. However, the combination of the airplane’s exceedance of the maximum takeoff gross weight and the high-density altitude likely resulted in degraded airplane climb performance and increased the time required to reach a suitable altitude to maintain clearance from the surrounding terrain.

Factual Information

HISTORY OF FLIGHT On July 1, 2021, about 1149 mountain daylight time, a Cessna 172R airplane, N2388L, was substantially damaged when it was involved in an accident near Missoula International Airport (MSO), Missoula, Montana. The pilot and passenger were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot did not file a Federal Aviation Administration flight plan or inform family members of the airplane’s destination. Recorded air traffic control audio captured the pilot receiving a clearance for a departure on runway 26. The pilot read back the clearance. No additional communication between the pilot and the controller was recorded. Automatic dependent surveillance-broadcast (ADS-B) data captured the first 5 minutes 48 seconds of the flight. The data revealed that the airplane departed MSO about 1141 and proceeded on a southwesterly heading at a groundspeed of about 70 to 75 knots. About 3 minutes later, the airplane initiated a right turn onto a westerly heading toward the Grave Creek Mountain Range, climbed to an altitude of 3,850 ft mean sea level (msl), and maintained a groundspeed of about 70 to 75 knots. At 1143:56, the airplane’s groundspeed decreased to about 68 knots and remained at that speed until the end of the recorded data 3 minutes 23 seconds later. The last recorded ADS-B target, at 1147:19, showed that the airplane was at an altitude of 5,225 ft msl (678 ft above ground level), on a magnetic heading of 271°, and about 3.3 miles east of the accident site. See figure 1. The terrain elevation near the last ADS-B point was about 4,547 ft msl. Figure 1. Overhead view of the flight track (in red) and the direction of travel (blue arrows). According to a ground support attendant at the fixed-base operator at the departure airport, the pilot requested that the fuel tanks be filled “all the way to the top.” The attendant reported that he added 28.5 gallons of fuel to the airplane. He stated that the pilot told him that he would be flying somewhere remote but did not specify where. AIRCRAFT INFORMATION The airplane’s weight for the flight was about 2,518 pounds. According to the Cessna 172R Pilot’s Operating Handbook, the maximum takeoff gross weight of the airplane was 2,450 pounds. The rate of climb, at maximum takeoff gross weight, at a pressure altitude of 6,000 ft and an airspeed of 74 knots was 415 ft per minute at 20°C and 360 ft per minute at 40°C. The stall speed for the flaps-up, power-off configuration was 51 knots calibrated airspeed. METEOROLOGICAL INFORMATION The density altitude for MSO about the time of the accident was calculated to be 5,917 ft. No SIGMET advisories for turbulence were active for the accident location at the accident time. No graphical AIRMET advisories (which are issued 3 hours apart) were active for the accident location at either 0900 or 1200 on the day of the accident. The Geostationary Operational Environmental Satellite-17 depicted mostly clear conditions across the region where the accident occurred. WRECKAGE AND IMPACT INFORMATION The airplane came to rest on a steep south-facing slope within a tree-covered canyon in the Grave Creek Mountain range (see figure 2) , on a magnetic heading of 040° and about 130° to the right of the last ADS-B data point. The valley was surrounded on three sides by higher elevation terrain. Figure 2. Google Earth image showing the last ADS-B data point and the accident site. All terrain at or below 5,225 ft msl (the airplane’s altitude at the last data point) appears in yellow. The first identified point of impact was a severed tree trunk about 30 ft above ground level. Tree damage ahead of the wreckage was oriented from the south at a 30° to 45° angle. The terrain slope was about 45°. All major components of the airplane were found in a small debris area immediately around the airplane, consistent with a lowenergy, nearvertical impact. According to the impact angle of the tree to the left wing, the airplane was about 30° nose down with little bank angle at the time of impact. Flight control continuity was established for all control surfaces. Postaccident examination of the airframe and engine revealed no mechanical malfunction or failures that would have precluded normal operation.

Probable Cause and Findings

The pilot’s failure to maintain airspeed and exceedance of the airplane’s critical angle of attack, which resulted in an aerodynamic stall at an altitude too low for recovery.


Source: NTSB Aviation Accident Database

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